The present invention relates to a process for the preparation of a water and oil emulsion comprising a phospholipoprotein containing material, which has been modified by phospholipase A, and at least one native starch based thickening agent. More particularly the invention relates to a process for the preparation of an oil-in-water emulsion of the mayonnaise, French dressing or salad dressing type.
There is an increasing demand for milder, preservative-free oil-in-water emulsion based products, which have not been subjected to severe heat treatments, but at the same time have an acceptable taste and good keeping properties. In order to prepare these products, the manufacturer faces a number of sometimes conflicting requirements. If the product has to be mild, the use of chemical preservatives to inhibit the growth of unacceptable microorganisms is almost unavoidable. If on the other hand the product should be free of these chemical preservatives, one has to resort to the use of such amounts of acid in order to arrive at an acceptable shelf life of the product, that the taste of the product is unacceptably harsh.
Mild products, which are free of chemical preservatives treatment, but upon heating above 60.degree. C.-70.degree. C., the egg yolk in oil-in-water emulsions looses its emulsifying properties, which results in coarsening of the emulsion, followed by oil exudation. Products based on milk protein instead of egg yolk as emulsifying agent are generally heat-stable at 60.degree. C.-70.degree. C., but lack the desired creamy taste impression originating from the egg yolk. With salad dressing an additional problem is met. Salad dressing resembles mayonnaise in that it is also an oil-in-water emulsion, but in addition to egg yolk it contains starch based thickening agents and gums. These thickeners usually are chemically modified starches, which however are expensive and moreover there is an increasing demand to have these chemically modified starches replaced by native starches. The use of native starches entails a number of difficulties, however, because they are more sensitive to temperature, time and shear conditions during gelatinization. Moreover during storage of the dressings prepared with native starches, gel formation (thickening) and as a consequence water separation (syneresis) often occurs due to retrogradation of the starch, leading to unacceptable products.